The invention relates to methods and equipment for providing location services in a telecommunications system comprising a packet radio network, and for the use of the packet radio network as a bearer for location information. Mobile communications systems provide mobile users with means to communicate from an arbitrary location within a Public Land based Mobile Network PLMN. Initially, mobile communications systems offered more or less the same services as do wired communications systems, i.e. voice calls, data calls and fax calls. The ever-changing location of the mobile user has been seen more as a necessary evil than a useful piece of information which the wired communications systems cannot deliver. A more modern vision is that by making full use of the user's location mobile communications systems can achieve competitive advantages over wired communications systems. This information can be used for customizing certain value-added services according to the user's location. Such location-specific value-added services include weather forecasts, entertainment programmes, timetables, navigation and locating a mobile user in an emergency. Additionally, the user's location can also be used for law-enforcement purposes.
In a conventional cellular mobile communications system, such as GSM (Global System for Mobile Communication), a mobile station can be located within one cell if the mobile station is having an ongoing call. Without such an ongoing call the location is known only within a location area, which typically comprises several cells. Even if the location is known within one cell, there is still considerable ambiguity concerning the location, considering that the diameter of a GSM cell can be as large as 70 km. More precise location service is the subject of standardization work being performed in a US standardization group called T1P1. There are several known methods by which a mobile station can be located with reasonable precision. For example, a mobile station can have an integrated GPS receiver, whereby it can determine its own coordinates and send them to the network. A mobile station without an integrated GPS receiver can be located e.g. by triangulation using three base stations. Details of the location procedure are not relevant to this invention, however, and a reference is made to the relevant T1P1 specifications.
Within the context of this application, the following conventions will be used. ‘Location management’ refers to the task of tracking the location of a mobile station in terms of location/routing areas and cell/network element identifiers. Thus, location management is performed in any mobile communications system, and it is a necessary task for routing calls to a mobile subscriber. In contrast, ‘location service’ (LCS) refers to the task of tracking the location of a mobile station in terms of geographical coordinates. This task is not necessary for routing calls. Rather, it is a value-added service, or it can be used for producing value-added services.
A problem with prior art location service systems is that packet radio subscribers are completely ignored. There are no known methods to locate a mobile station with a subscription only to a packet radio network, such as GPRS (General Packet Radio Service). A brute-force approach would be to implement a separate location service for the packet-switched network, but this would result in duplicating several network elements. There are no known signalling conventions enabling the use of the location service for the circuit-switched network also in the packet-switched network.